The present invention is directed toward reticles and methods of forming and employing the reticles.
Reticles are used in the semiconductor industry to form semiconductor devices having device features. There is a continuing effort to increase device density by scaling down device size, and state of the art devices currently have device features with dimensions well below one micron. Most reticles contain subarray areas containing the patterns for the memory features of the device. As the features size decreases, edge of array effects are observed. The edge of array effects are generally seen as critical dimension differences between the edge or corner of the subarray area and the subarray area a distance from the edge.
The edge of array effects may be caused by a number of factors. For example, process loading during the manufacture of a reticle may occur. Process loading during reticle manufacture may introduce error into the subarray area because the entire reticle pattern may contain dense and less dense or open areas. Similarly, process loading during wafer processing may occur that causes error to be introduced into the subarray area on the wafer. Stray light from less dense areas of a reticle can cause bulk exposure in a clear field reticle. Additionally, reticles may suffer from underexposure due to large dark areas of a dark field reticle to prevent underexposure.
Thus, there remains a need in the art for reticle patterns that address edge of array effects, and there remains a need in the art for methods of forming and using such reticle patterns.
The present invention relates to reticles and methods of forming and using reticles. In accordance with one embodiment of the present invention, a reticle is provided. The reticle comprises a reticle substrate having a reticle pattern, and the reticle pattern comprises at least one subarray area and at least one periphery area. The at least one subarray area is defined by densely patterned subarray features, and the at least one periphery area is defined by open areas that lie outside the at least one subarray area. The open areas defining the at least one periphery area have a transmission pattern etched therein.
In accordance with another embodiment of the present invention, a system for patterning a radiation sensitive layer comprising a source of electromagnetic radiation and a reticle is provided. The reticle comprises a reticle substrate having a reticle pattern, and the reticle pattern comprises at least one subarray area and at least one periphery area. The at least one subarray area is defined by densely patterned subarray features, and the at least one periphery area is defined by open areas that lie outside the at least one subarray area. The open areas defining the at least one periphery area have a transmission pattern etched therein.
In accordance with yet another embodiment of the present invention, a method of forming a reticle is provided. The method comprises providing a reticle blank; patterning the reticle blank to form a reticle pattern, wherein the reticle pattern comprises at least one subarray area and at least one periphery area, the at least one subarray areas is defined by densely patterned subarray features, and the at least one periphery area is defined by open areas that lie outside the at least one subarray area; and etching said open areas defining said at least one periphery area to form a transmission pattern.
In accordance with another embodiment of the present invention, a method of patterning a radiation sensitive layer is provided. The method comprises providing a reticle, and the reticle comprises a transparent reticle substrate having a reticle pattern. The reticle pattern comprises at least one subarray area defined by densely patterned subarray features and at least one periphery area defined by open areas. The open areas defining the at least one periphery area lie outside the at least one subarray area, and the open areas defining the at least one periphery area contain a transmission pattern formed therein. The method further comprises exposing a radiation sensitive layer with the reticle such that the radiation sensitive layer is exposed the reticle pattern. The densely patterned subarray features defining the at least one subarray area are patterned on the radiation sensitive layer in areas exposed to the at least one subarray area, and the radiation sensitive layer is not patterned in areas exposed to the transmission pattern in the at least one periphery area.